1. Field of the Invention
The present invention relates to a process for processing color photographic materials. More particularly, it relates to a process for processing color photographic materials using a color developer containing a novel antioxidant harmless to the human body in place of hydroxylamine.
2. Description of the Prior Art
Photographic processing steps for obtaining color photographic images from silver halide color photographic light-sensitive materials comprise at least two fundamental steps, that is, a color-developing step and a silver-removing step. In the color-developing step wherein color images are formed through a coupling reaction between an oxidation product of a developing agent produced upon reduction of silver halide and a dye-forming coupler, a color developer containing an aromatic primary amine developing agent is usually used. In order to prevent a reduction in developing power resulting from air oxidation with the lapse of time, the color developer usually contains a sulfite and hydroxylamine as antioxidants.
In color development, fog called "color fog" or "stain" is often formed. This phenomenon cannot be prevented with an ordinarily employed, so-called anti-fogging agent such as an alkali metal halide, 1-phenyl-5-mercaptotetrazole, benzotriazole, 5-nitrobenzimidazole, etc. "Color fog" is considered to be caused by an oxidation product formed as a result of a color developing agent being partly oxidized, i.e., semiquinone or quinoneimine derived from an aromatic primary amine, quinonemonoimine formed via a deamination reaction, quinonemonoimine sulfite adduct, etc. Such color fog causes a reduction in color purity in multilayer color light-sensitive materials as well as formation of color stain in the non-image areas. Color fog increases when the color developer is exhausted with the lapse of time or by repeated use.
Hydroxylamine plays an important role with respect to prevention of color fog. Color fog seriously increases when no hydroxylamine is present or when the hydroxylamine has been decomposed. Therefore, hydroxylamine has so far been an indispensable ingredient in a color developer. However, hydroxylamine has the defect that, when heavy metal ion such as iron or copper ion is also present in the developer, the decomposition of hydroxylamine is markedly accelerated. Contamination of the developer with iron ion or copper ion results from various ion sources such as water, vessels and the apparatus used for preparing the developer. The vessel for storing the developer, and pumps, troughs and the apparatus used for development. When decomposed, hydroxylamine loses its antioxidizing action and, in addition, the decomposition products thereof further increase fog. Attempts have been made to add aminopolycarboxylic acids such as ethylenediaminetetraacetic acid, nitrilotriacetic acid, etc. to the developer in order to mask heavy metal ions. However, heavy metal chelates of nitrilotriacetic acid and ethylenediaminetetraacetic acid rather additionally accelerate the decomposition of hydroxylamine.
In addition, hydroxylamine is so harmful to the human body (P. G. Stecher, The Merck Index-An Encyclopedia of Chemicals and Drugs, 8th Ed. (1953)) that hydroxylamine and the water-soluble salt thereof are specified as weak poisons by Japanese law for managing poisons. Therefore, special care has to be exercised in handling color developers containing hydroxylamine in commercial photographic processings. In particular, such a developer is not suitable for amateur use at home.
Thus, it has been desired to develop an antioxidant replacing hydroxylamine.
2-Anilinoethanol and dihydroxyalkene are suggested in U.S. Pat. Nos. 3,823,017 and 3,615,503, respectively as an anti-oxidant for replacing hydroxylamine. However, both of these compounds are unstable themselves and do not have the effect of preventing color fog at all.
On the other hand, with respect to a developer (for black-and-white photography) containing hydroquinone or N-alkyl-p-aminophenol as a developing agent, saccharose (sucrose) is known as an antioxidant. However, saccharose is almost useless as an antioxidant for a color developer containing an aromatic primary amine as a developing agent.
Ascorbic acid and the derivatives thereof are known as antioxidants for a black-and-white developer and for a color developer. They possess, however, the defect of inhibiting coloration and causing a reduction in color density. Thus they are inferior to hydroxylamine for use in a color developer.